1. Field of the Invention
This invention relates to a bio-chip, more particularly to a bio-chip adapted for separating and concentrating particles in a solution.
2. Description of the Related Art
Raman spectroscopy has become a popular technique for determining microorganism species. Unlike conventional methods for microorganism detection that need professionals having particular skills to perform, for example, DNA extraction, nucleic acid detection, fluorescent labeling, or biochemistry analysis, microorganism species can be determined by directly comparing spectroscopic spectrum of a sample to be detected with reference spectra.
While Raman spectroscopy is first adopted for microorganism detection, a high concentration (above 1012 colony forming units (CFU)/ml) of a target microorganism is required for generating a signal that is strong enough to be detected, and characteristic peaks of the spectroscopic spectrum are not really significant. Also, a further purification process for samples is required to perform Raman spectroscopy detection so as to obtain the spectroscopic fingerprint specific to a target microorganism.
It is reported to utilize a substrate having a roughened surface to trap target microorganism thereon for performing Raman spectroscopy technique, so that a surface-enhanced Raman spectroscopic (SERS) signal is obtained. However, such method is not applicable to unpurified samples.
A conventional method to concentrate a target microorganism in a purified sample solution for Raman spectroscopy detection is to generate ring stains (also called “coffee ring”) from drops of the purified sample solution. The target microorganism in the sample drops are subjected to surface tension and cohesive forces and thus are concentrated in the ring stains while drying the sample drops. However, the method is still not applicable to unpurified samples.
From the methods describing above, a major obstacle while performing Raman spectroscopic detection relies on that a purified sample is needed instead of an actual sample, such as human blood containing variety of non-target materials, for instance, blood cells, proteins, and so forth. The non-target materials would generate spectroscopic fingerprints as well, thereby interfering the spectroscopic fingerprint of the target microorganism. Moreover, drying time for generating the ring stain is relatively long, e.g., if the volume of the sample is greater than 10 μL, the drying time is about half an hour.
Recently, a method for capturing target microorganism by utilizing a chemical/antibody-modified silver/anodic aluminum oxide (AAO) substrate is disclosed. The Ag/AAO substrate is modified with Vancomycin thereon for capturing bacteria from the mixture of bacteria-blood cells, and SERS signal is thus enhanced. However, it takes a large amount of time for the target bacteria to be binding with Vancomycin on the substrate, and not all bacteria are capable of being recognized by Vancomycin.
From describing herein above, the applicant thinks that adopting a bio-chip, which is capable of separating and concentrating the target particles in actual samples (i.e., mixture samples), combined with Raman spectroscopy is the right track for developing an ultra-fast and precise detection method of microorganism species in the actual samples without further purification. However, in Taiwanese Patent Application No. 100110372, No. 098123205, NO. 099100678, and No. 095139596, methods or chips disclosed therein have several disadvantages such as requirement of high microorganism concentration (106 CFU/ml to 102 CFU/ml), relatively small detecting area, requirement of further purification for target microorganisms, and low selectivity for the target microorganisms. Thus, there is a need in the art to provide a bio-chip that can overcome the aforesaid drawbacks.